Multiple-sensor array touch-sensing system and related method

A touch-sensing system, comprising:

• a cover stack having an outer surface that can be touched by a finger, the cover stack having a longitudinal direction along which the finger can touch and slide on the outer surface;
• piezoelectric capacitors mechanically coupled to the cover stack at its inner interface, the cover stack overlying the piezoelectric capacitors, the piezoelectric capacitors comprising one or more piezoelectric members;
• a first array of at least two of the piezoelectric capacitors configured as piezoelectric ultrasonic transducers (PUTs);
• a second array of at least two of the piezoelectric capacitors configured as piezoelectric force-measuring elements (PFEs);
• and
• a signal processor configured to receive PUT array signals from the PUTs and PFE array signals from the PFEs,
• wherein:
• each of the PUTs is configured as a transmitting-type PUT and/or a receiving-type PUT, the receiving-type PUTs numbering at least two in the first array;
• the first array and the second array extend along at least one direction including the longitudinal direction;
• the transmitting-type PUTs are configured to transmit ultrasound waves towards the cover stack in a predetermined frequency range, the ultrasound waves propagating along a normal direction approximately normal to a plane of the one or more piezoelectric members;
• the receiving-type PUTs are configured to receive the ultrasound waves from the cover stack in the predetermined frequency range;
• the PUT array signals are generated in accordance with the ultrasound waves received at the receiving-type PUTs;
• the PFE array signals are obtained from voltage signals generated at the PFEs in response to a low-frequency deformation of the cover stack;
• the signal processor is configured to calculate, from the PUT array signals, PUT centroid data;
• the signal processor is configured to calculate, from the PFE array signals, PFE centroid data;
• the signal processor is configured to determine, whether a touch event on the cover stack has occurred;
• and
• the signal processor is configured to determine an estimated touch position on the cover stack by combining applicable centroid data comprising the PUT centroid data and the PFE centroid data, the PUT centroid data being apportioned a PUT fractional weight w(PUT), the PFE centroid data being apportioned a PFE fractional weight w(PFE).